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rephrase tutorial on Map

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Benoit Jacob 2009-10-31 14:37:11 -04:00
parent 3ae4e3880f
commit 5ba19a53a6
1 changed files with 15 additions and 9 deletions
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doc/C01_QuickStartGuide.dox
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@ -278,18 +278,24 @@ Of course, fixed-size matrices can't be resized.
\subsection TutorialMap Map
Any memory buffer can be mapped as an Eigen expression:
<table class="tutorial_code"><tr><td>
Any memory buffer can be mapped as an Eigen expression using the Map() static method:
\code
std::vector<float> stlarray(10);
Map<VectorXf>(&stlarray[0], stlarray.size()).setOnes();
int data[4] = 1, 2, 3, 4;
Matrix2i mat2x2(data);
MatrixXi mat2x2 = Map<Matrix2i>(data);
MatrixXi mat2x2 = Map<MatrixXi>(data,2,2);
VectorXf::Map(&stlarray[0], stlarray.size()).squaredNorm();
\endcode
Here VectorXf::Map returns an object of class Map<VectorXf>, which behaves like a VectorXf except that it uses the existing array. You can write to this object, that will write to the existing array. You can also construct a named obtect to reuse it:
\code
float array[rows*cols];
Map<MatrixXf> m(array,rows,cols);
m = othermatrix1 * othermatrix2;
m.eigenvalues();
\endcode
In the fixed-size case, no need to pass sizes:
\code
float array[9];
Map<Matrix3d> m(array);
Matrix3d::Map(array).setIdentity();
\endcode
</td></tr></table>
\subsection TutorialCommaInit Comma initializer